The present invention relates to an electric rotating machine and a method of connecting feeding lead wires thereto.
As disclosed in Japanese Patent Prepublication No. 7036/1991, a conventional rotary machine has increased the limit of elasticity and the resistance-to-compression-plastic-deformation of the linear rising part of each lead wire by cold-pressing the lead wire so that the linear rising part of the lead wire may be harder than the other part of the lead wire, machining and bending the lead wire, and welding the linear rising part of the lead wire to a connection member by electron beams. Or the conventional rotary machine has increased the limit of elasticity and the resistance-to-compression-plastic-deformation of the linear rising part of each lead wire by connecting the lead wire to a connection member by welding or brazing, cold-pressing the connected lead wire so that the linear rising part of the lead wire may be harder than the other part of the lead wire, then machining and bending the lead wire.
However, the conventional connecting method makes the whole part of the lead wire have an approximately identical thickness. Therefore, during rotation of the electric rotating machine, an excessive centrifugal force concentrates on the joint between the linear rising part of the lead wire and the connection member, that is, the part which was softened by electron-beam welding. This allows plastic deformation on the joint. The latter connecting method in the above description which cold-presses the linear rising part of the lead wire after welding or brazing cannot be free from hardening not only the welded or brazed part but also the other part of the lead wire. As the result, the toughness of the non-welded part of the lead wire falls and becomes fragile. In an extreme case, the part may be broken.
A main object of the present invention is to provide an electric rotating machine and a method of connecting feeding lead wires thereto, which can increase the resistance to centrifugal forces of the lead wire without controlling the hardness of the lead wire by post-processing such as cold pressing and suppress plastic deformation of the joint between the lead wire and the joint conductor.
The present invention is basically characterized by concentrating stresses due to excessive centrifugal forces during rotation of the electric rotating machine to any other part of the lead wire than the joint between the lead wire and the joint conductor and preventing said other part of the lead wire from being softened by welding or brazing of the joint.
Concretely, to concentrate stresses due to excessive centrifugal forces during rotation of the electric rotating machine to any other part of the lead wire than the joint between the lead wire and the joint conductor, the present invention forms, on the lead wire, a first part to be connected to said joint conductor, a second part thinner than said first part, and a third part which is between said first and second parts and has the thickness changing from the thickness of said first part to the thickness of the second part. Further, to prevent said other part of the lead wire from being softened by welding or brazing of the joint, the present invention welds by electron beams or brazes the first part of the lead wire to the joint conductor while cooling the lead wire.
Here, the thickness of the first part and the thickness of second part represent distances of opposite surfaces along the longitudinal axis of the lead wire except surfaces perpendicular to the curved surfaces.
When the feeding lead wire in accordance with the present invention is applied to an electric rotating machine, the stress due to the excessive centrifugal force during rotation concentrates on the third part of the feeding lead wire. In other words, the third part of the lead wire increases its thickness toward the first part and the cross-section of the third part perpendicular to the longitudinal axis of the lead wire increases toward the first part. In other words, the third part varies its shape. Further, as the third part of the feeding lead wire will not be softened by welding or brazing of the joint, the third part can be kept as hard as the second part of the lead wire. Further the stresses due to excessive centrifugal forces during rotation of the electric rotating machine concentrate to this third part and weakened. This can protect the first part of the lead wire which is connected to the joint conductor from concentration of the stresses and suppress the plastic deformation of the first part.
Further, as the third part of the feeding lead wire will not be softened when the first part of the lead wire is welded or brazed to the joint conductor, the limit of elasticity of the third part can remain unchanged. In other words, the hardness of the second and third parts of the feeding lead wire can be greater than the hardness of the joint between the first part and the joint conductor. Therefore, the third part can fully stand the stresses due to excessive centrifugal forces.
Although the first part of the feeding lead wire is softened by electron-beam-welding or brazing, the first part is thicker than the second and third parts of the lead wire and wider than the second and third parts in the cross-section perpendicular to the longitudinal axis of the lead wire. Therefore, the lead wire can fully secure the resistance to the stresses due to excessive centrifugal forces.